The subject matter disclosed herein relates generally to magnetic resonance imaging (MRI) systems and, more particularly, to systems and methods for performing diffusion spectrum imaging (DSI) with an MRI system.
In general, magnetic resonance imaging (MRI) examinations are based on the interactions among a primary magnetic field, a radiofrequency (RF) magnetic field and time varying magnetic gradient fields with gyromagnetic material having nuclear spins within a subject of interest, such as a patient. Certain gyromagnetic materials, such as hydrogen nuclei in water molecules, have characteristic behaviors in response to external magnetic fields. The precession of spins of these nuclei can be influenced by manipulation of the fields to produce RF signals that can be detected, processed, and used to reconstruct a useful image.
DSI is an imaging technique for generating diffusion information that may be utilized in the clinical evaluation of various diseases, for example, traumatic brain injuries and/or multiple sclerosis. In DSI, the information is encoded in both q-space or diffusion space, as well as in image space. The q-space information may be used to characterize the diffusion properties of water molecules. More specifically, by applying a series of diffusion encoding gradient pulses in multiple directions and strengths, a three-dimensional characterization of the water diffusion process may be generated at each spatial location or image voxel. The MR signal in q-space is generally related to the water displacement probability density function at a fixed echo time by the Fourier transform. The diffusion information encoded in q-space may be separated into both angular and radial components. The angular component reflects the underlying tissue anisotropy, whereas the radial component (e.g., the radial kurtosis) provides information about the eventual geometric restrictions in the diffusion process.
Conventional DSI techniques typically provide useful information about the diffusion properties of water in an organ of interest, such as the brain, but are associated with a variety of drawbacks. For example, the high dimensionality of DSI often requires a patient to be positioned in an MRI scanner for a long period of time. For further example, the reconstructed MR images may include noise that makes it more difficult for a clinician to obtain useful information from the acquired images. Accordingly, there exists a need for improved systems and methods that address these drawbacks.